Heating apparatus of washing machine and washing method thereof

ABSTRACT

A heating apparatus of a washing machine and a washing method thereof. The heating apparatus includes a circulation channel installed outside a tub for connecting one side of the tub to the other side of the tub, and an orifice, water drop supply device for supplying water, an air blower for circulating the water, and a heater, which are sequentially installed in the circulation channel. The heating apparatus supplies steam or hot wind to the tub in a washing or rinsing operation, thereby improving the washing capacity of the washing machine, minimizing the time taken to perform the washing or rinsing operation and an energy consumption rate, and allows the washing machine to perform a drying operation using hot wind without any additional element, thereby diversifying its functions and minimizing production costs.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a washing machine, and moreparticularly to a heating apparatus of a washing machine, which provideshot wind or steam in a washing or rinsing mode, and is also operated ina drying mode, and a washing method thereof.

2. Description of the Related Art

FIG. 1 is a longitudinal-sectional view of a conventional washingmachine.

The conventional washing machine comprises a cabinet 2 provided with adoor 1 installed on the front door thereof, a tub 4 placed in thecabinet 2 and supported by a damper 3, a drum 6 rotatably installed inthe tub 4 and provided with a plurality of water pores 5 formed throughthe cylindrical surface thereof, and a driving device 10 installedoutside the tub 4 and connected to the drum 6 by a rotary shaft forrotating the drum 6.

A water supply pipe 12 provided with a water supply valve 14 for guidingwash water to the tub 4 is connected to the upper part of the tub 4.

The water supply pipe 12 passes through a detergent container 16containing a detergent. Accordingly, when wash water is supplied to thetub 4 through the water supply pipe 12, the detergent contained in thedetergent container 16 is supplied together with the wash water to thetub 4.

A drainage pipe 18 for guiding the wash water of the tub 4 to theoutside is connected to the lower part of the tub 4, and the drainagepump 20 is installed on the drainage pipe 18.

Lifters 22, for lifting up laundry placed in the drum 6 and thendropping the laundry by gravity when the drum 6 containing the laundryis rotated, are formed on the inner wall of the drum 6.

Further, a washing heater 30 is installed in the washing machine,thereby heating the wash water supplied to the tub 4 to a temperaturesuitable to wash the laundry and generating steam for sterilizing thelaundry.

Generally, the washing heater 30 is installed on the bottom of theinside of the tub 4.

Further, a drying apparatus 40 for drying the laundry using hot wind fora short period of time, rather than naturally drying the laundry, afterthe washing of the laundry is completed.

The drying apparatus 40 includes a condensing duct 42 connected to thelower part of the tub 4, a drying duct 44 for connecting the condensingduct 42 and the upper part of the tub 4, an air blower 46 for generatingair-blowing force from the condensing duct 42 to the drying duct 44, acooling water channel 48 for supplying cooling water 42′ to thecondensing duct 42, a cooling water valve 50 for opening and closing thecooling water channel 48, and a drying heater 52 installed in the dryingduct 44.

Generally, in a washing method of the above-described washing machine, awashing mode for removing dirt from the laundry, a rinsing mode forrinsing the laundry with clean wash water, and a dehydrating mode foreliminating moisture from the laundry are sequentially operated. Theabove modes may be selectively performed according to user' selection.

In case that the washing heater 30 is installed in the washing machine,the washing heater 30 heats the wash water to a temperature suitable towash the laundry in the washing or rinsing mode, and heats the washwater to a temperature higher than the preceding temperature to performsteam washing.

In case that the drying apparatus 40 is installed in the washingmachine, the washing method is operated also in a drying mode forcompletely drying the laundry using hot wind.

In the drying mode, the air blower 46 of the drying apparatus 40 isoperated to circulate air into the tub 4, the condensing duct 42, thedrying duct 44, and the tub 4 in order, and the condensing duct 42condenses the air of high humidity in the tub 4 using cooling water. Thecondensed air is heated by the drying heater 52 of the drying duct 44,thereby being changed into hot wind. Here, the cooling water supplied tothe condensing duct 42 is supplied to the tub 4, and is then dischargedto the outside through the drainage pipe 18.

In the conventional washing machine, when the temperature of the washwater increases or a steam-washing operation is performed, the washwater is first supplied to the tub 4 and heated by the washing heater30, and laundry is heated by the heated wash water. Accordingly, theconventional washing machine is disadvantageous in that the time takento perform the washing or rinsing operation is elongated and an energyconsumption rate is increased.

Further, the washing machine, which is performed in the dryingoperation, requires the drying apparatus 40, operated in the same manneras the washing heater 30, thereby increasing the production costs andhaving an increased size.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the aboveproblems, and it is an object of the present invention to provide aheating apparatus of a washing machine, which increases the temperatureof wash water supplied to a tub in a washing or rinsing operation, so asto be suitable to wash the laundry, or minimizes the time and energyconsumption taken to perform the washing or rinsing operation of asteam-washing mode, and a washing method thereof.

It is another object of the present invention to provide a heatingapparatus of a washing machine, which has a drying function as well asincreases the temperature of wash water or performs a steam-washingmode, and a washing method thereof.

In accordance with one aspect of the present invention, the above andother objects can be accomplished by the provision of a heatingapparatus of a washing machine comprising: a circulation channel forconnecting one side of a tub to the other side of the tub so that air ofthe tub is circulated therethrough; an air blower installed in thecirculation channel for generating air-blowing force; a heater installedin the circulation channel for heating air of the circulation channel;and water drop scattering device installed in the circulation channelfor scattering water drops in air blown by the heater so that steam issupplied to the tub.

The circulation channel may include a condensing duct connected to oneside of the tub for condensing the air of the circulation channel; and adrying duct connecting the condensing duct to the other side of the tuband including the heater installed therein.

The water drop scattering device may be installed in the condensingduct.

The water drop scattering device may include water drop supply deviceincluding a nozzle for spraying water drops into the circulationchannel; and an orifice installed in the circulation channel forscattering the water drops supplied into the circulation channel.

The orifice may be obtained by forming a protrusion along the inner wallof the air blower.

The orifice may have a shape such that the width of the orifice isgradually narrowed and then gradually broadened in the direction ofblowing air of the air blower.

The water drop scattering device may be located in front of the airblower in the direction of blowing air of the circulation channel.

In accordance with a further aspect of the present invention, there isprovided a heating apparatus of a washing machine comprising: acondensing duct connected to one side of a tub; a drying duct connectingthe condensing duct to the other side of the tub, and including a heaterinstalled therein; an air blower for generating air-blowing force in thedirection from the condensing duct to the drying duct; a nozzleinstalled in the condensing duct for spraying water into the condensingduct; and water drop scattering device installed in the condensing duct,and including an orifice for scattering the water sprayed into thecondensing duct.

The orifice may have a shape such that the width of the orifice isgradually narrowed and then gradually broadened in the direction ofblowing air of the air blower.

In accordance with another aspect of the present invention, there isprovided a washing method of a washing machine comprising: circulatingair of a tub into a circulation channel in a washing or rinsingoperation, and spraying and scattering water in a dropping state intothe circulation channel; producing steam by operating a heater installedin the circulation channel; and supplying the steam to the tub.

The washing method may further comprise: supplying a larger quantity ofwater in a drying operation to the circulation channel than that of thewashing or rinsing operation during the circulation of the air of thetub into the circulation channel; condensing the air of the circulationchannel, producing hot wind by heating the condensed air using theheater; and supplying the hot wind to the tub.

The velocity of air blown into the circulation channel when the steam issupplied to the tub may be higher than the velocity of air blown intothe circulation channel when the hot wind is supplied to the tub.

Wash water may be supplied to the tub through the circulation channel inthe washing or rinsing operation.

In accordance with yet another aspect of the present invention, there isprovided a washing method of a washing machine comprising: circulatingair of a tub into a circulation channel in a washing or rinsingoperation; heating the air of the circulation channel to produce hotwind; and supplying the hot wind to the tub.

Wash water may be supplied to the tub through the circulation channel inthe washing or rinsing operation.

The washing method may further comprise drying laundry of the tub usingthe hot wind in a drying operation.

Water drops may be sprayed selectively into the circulation channel andscattered so that steam is supplied to the tub.

The velocity of air blown into the circulation channel when the steam issupplied to the tub may be higher than the velocity of air blown intothe circulation channel when the hot wind is supplied to the tub.

A larger quantity of water when the hot wind is supplied to the tub maybe supplied to the circulation channel than when the water drops aresprayed into the circulation channel.

The washing method may further comprise drying laundry of the tub usingthe hot wind in a drying operation.

In the heating apparatus of a washing machine and the washing methodthereof in accordance with the present invention, steam or hot wind issupplied to an upper part of a tub in a washing or rinsing operation soas to directly heat wash water and laundry, thereby reducing the timetaken to perform the washing or rinsing operation and an energyconsumption rate, and improving a washing capacity.

Further, in the heating apparatus of a washing machine and the washingmethod thereof in accordance with the present invention, hot wind isproduced in the same manner as the washing or rinsing operation and issupplied to the tub so as to dry the wet laundry, thereby diversifyingthe function of the heating apparatus without additional cost andminimizing production costs of the heating apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a longitudinal-sectional view of a conventional washingmachine; and

FIG. 2 is a longitudinal-sectional view of a washing machine inaccordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, with reference to the annexed drawings, an embodiment of a heatingapparatus of a washing machine and a washing method thereof inaccordance with the present invention will be described in detail.

Although the present invention may comprises a plurality of embodimentsof a heating apparatus of a washing machine and a washing methodthereof, the most preferred embodiment will be described hereinafter.The essential structures of the heating apparatus of the washing machineof the present invention and the washing method thereof are the same asthose of the conventional heating apparatus of the washing machine andthe conventional washing method thereof, and detailed descriptionthereof will thus be omitted.

FIG. 2 is a longitudinal-sectional view of a washing machine inaccordance with the present invention.

The washing machine as shown in FIG. 2 comprises a tub 52 placed in thecabinet 50 and supported by a damper 51, a drum 54 rotatably installedin the tub 52 and provided with a plurality of water pores 54′ formedthrough the cylindrical surface thereof, a driving device 56 forrotating the drum 54, a water supply device 58 for supplying wash waterto the tub 52, a drainage device 60 for discharging the wash water ofthe tub 52, and a heating apparatus 70 for supplying steam to the tub52.

The heating apparatus 70 includes a circulation channel 72 installedoutside the tub 52 for connecting the upper and lower parts of the tub52 so that the air of the tub 52 is circulated, an air blower 74installed in the circulation channel 72 for blowing the air of thecirculation channel 72 to the upper part of the tub 52, an electricheater 76 installed in the circulation channel 72 for heating the air ofthe circulation channel 72, and water drop scattering device 80,connected to the circulation channel 72 so that steam is supplied fromthe circulation channel 72 to the tub 52, for scattering water dropsover the air blown to the heater 76.

The air blower 74 is located on the upper part of the tub 52. The heater76, as shown by the arrows in FIG. 2, is placed in the rear of the airblower 74 in the direction of blowing the air of the circulation channel72. The water drop scattering device 80 is placed in front of the airblower 74 in the direction of blowing the air of the circulation channel72.

The water drop scattering device 80 includes water drop supply device 82for spraying the water into the circulation channel 72 in a droppingstate, and an orifice 86 placed in the circulation channel 72 forscattering the water drops sprayed into the circulation channel 72.

The water drop supply device 82 includes a water channel 81 forconnecting the circulation channel 72 to a water storage tank or a watertap, a water channel valve 83 installed on the water channel 81 foropening and closing the water channel 81, and a nozzle 84 connected tothe end of the water channel 81 such that the nozzle 84 is placed in thecirculation channel 72.

Preferably, the water channel valve 83 controls water passing throughthe water channel 81 to have a small amount so that the water dropsprayed from the nozzle 84 into the circulation channel 72 is easilyscattered.

The nozzle 84 is located in the rear of the orifice 86 in the directionof blowing the air of the circulation channel 72 so that the water dropssprayed from the nozzle 84 into the circulation channel 72 are scatteredby the orifice 86.

Preferably, the nozzle 84 is placed close to the air blower 74 so thatthe water drops sprayed from the nozzle 84 into the circulation channel72 are easily scattered by the air-blowing force of the air blower 74.More preferably, the air blower 74 is driven at a high speed so that theliquid drops sprayed from the nozzle 84 into the circulation channel 72are more easily scattered.

The orifice 86 is obtained by forming a protrusion 87 along the innerwall of the circulation channel 72 so as to partially narrow thecirculation channel 72. The protrusion 87 may be formed integrally withthe circulation channel 72, and may vary the size of the orifice 86.

Preferably, the orifice 86 has a shape such that the width of theorifice 86 is narrowed in the direction of blowing the air of thecirculation channel 72 to form a neck portion 86′ having the smallestdimensions and is then broadened again.

The heating apparatus 70 of the present invention further comprises aircondensing means connected to the circulation channel 72 for condensingair blown to the heater 76, thereby supplying hot wind of humidity lowerthan that of steam from the circulation channel 72 to the tub 52.

The air condensing means supplies cold water to the circulation channel72, thereby condensing the air in the circulation channel 72. However,since the water drop supply device 82 also supplies water, the heatingapparatus of the present invention condenses the air of the circulationchannel 72 using the water drop supply device 82 without the aircondensing means.

That is, when hot wind is supplied to the tub 52 compared to when steamis supplied to the tub 52, a larger quantity of water is supplied fromthe water drop scattering device 82 to the circulation channel 72 andthe air blower 74 is more slowly rotated. Then, the water supplied fromthe water drop supply device 82 to the circulation channel 72 is notscattered and flows along the circulation channel 72 toward the lowerpart of the tub 52, thereby condensing the air of the circulationchannel 72.

The above-described heating apparatus 70 for supplying steam and hotwind to the tub 52 selectively supplies one of steam and hot wind to thetub 52. The circulation channel 72 is divided into a condensing duct 71including the water drop scattering device 80 or the air condensingmeans, and a drying duct 73 including the heater 76. Preferably, thewater channel valve 83 controls the respective quantity of water whensteam is supplied to the tub 52 and when hot wind is supplied to the tub52.

The above heating apparatus 70 may be used to supply water to the lowerpart of the tub 52 through the water drop supply device 82 and thecirculation channel 72 regardless of the supply of steam or hot wind tothe tub 52.

Hereinafter, the function of the above-described heating apparatus 70will be described in detail.

In order to supply steam to the tub 52, the air blower 74 is operated sothat the air of the tub 52 is circulated through the circulation channel72. Then, the water drop supply device 82 is operated so that waterdrops are sprayed into the condensing duct 71 of the circulation channel72.

The water drops sprayed into the condensing duct 71 of the circulationchannel 72 are scattered by the difference of speeds of currentgenerated by the orifice 86 formed in the circulation channel 72. Here,in order to facilitate the scattering of the water drops sprayed intothe condensing duct 71 of the circulation channel 72, the air blower 74is operated at a high speed (approximately 3,000 rpm) and the waterchannel 81 is controlled such that a small amount of water flowstherethrough.

The air of the tub 52 is circulated into the circulation channel 72, andthe water drops are scattered in the condensing duct 71 of thecirculation channel 72. Simultaneously, the heater 76 is operated,thereby heating the air in which the water drops are scattered. Thus,steam is generated from the drying duct 73 of the circulation channel72, and is supplied to the tub 52.

In order to supply hot wind to the tub 52, in the same manner as thesupply of steam to the tub 52, the air blower 74 is operated so that theair of the tub 52 is circulated through the circulation channel 72, thewater drop supply device 82 is operated so that water drops are sprayedinto the condensing duct 71 of the circulation channel 72, and theheater 76 is operated so that the air of the drying duct 73 of thecirculation channel 72 is heated.

However, in order to cause the water, sprayed from the water drop supplydevice 82 to the condensing duct 71 of the circulation channel 72, toflow along the condensing duct 71 of the circulation channel 72 towardthe lower part of the tub 52, the operating speed of the air blower 74is lowered (approximately 2,000 rpm) and the water channel 81 iscontrolled such that a large quantity of amount of water flowstherethrough, compared to the supply of steam to the tub 52. Here, it ispreferable that cold water be supplied from the water drop supply device82 to the condensing duct 71 of the circulation channel 72.

In case that the heating apparatus 70 is operated as described above,when the air of the tub 52 is circulated along the circulation channel72, the air is condensed by the cold water in the condensing duct 71 ofthe circulation channel 72, and the condensed air is heated by theheater 76 in the drying duct 73 of the circulation channel 72, therebyproducing hot wind having a comparatively low humidity. The hot windproduced by the circulation channel 72 is supplied to the tub 52 by theair-blowing force of the air blower 74.

Hereinafter, washing and rinsing operations of a washing machinecomprising the above-described heating apparatus will be described indetail.

First, in the washing operation, wash water is supplied to the tub 52such that laundry in the drum 54 is sufficiently soaked in the washwater, and a detergent is dissolved in the wash water supplied to thetub 52 so that the laundry in the drum 54 is washed clean.

Here, the wash water may be supplied to the tub 52 through the watersupply device 58. Further, since the water drop supply device 82 alsoserves to supply water, the wash water may be supplied to the lower partof the tub 52 through the water drop supply device 82 and thecirculation channel 72. Otherwise, the wash water may be supplied to thetub 52 through the water supply device 58, the water drop supply device82, and the circulation channel 72. In case that the wash water issupplied to the tub 52 through the water drop supply device 82 and thecirculation channel 72, preferably, the air blower 74 is stopped so asnot to forcibly circulate the air of the tub 52 through the circulationchannel 72, and the heater 76 is not operated.

After a sufficient amount of wash water is supplied to the tub 52, thedrum 54 is rotated by the driving device 56. Then, the laundry in thedrum 54 is washed by the current of the wash water, the friction withthe tub 52, and the emulsification of the detergent.

During the washing operation, steam can be supplied to the tub 52through the heating apparatus 70. The steam supplied to the tub 52serves to directly heat the wash water supplied to the tub 52 and thelaundry placed in the drum 54, thereby easily removing dust from thelaundry and sterilizing the laundry similar to the boiling the laundry.Further, since steam permeates the laundry more rapidly than water, thesupply of the steam reduces the quantity of the wash water supplied tothe tub 52 compared to the non-supply of the steam under the conditionthat the quantity of water and the washing course are the same.

Alternately, during the washing operation, hot wind may be supplied tothe tub 52 through the heating apparatus 70, thereby heating the washwater supplied to the tub 52.

After the washing operation is completed, the wash water supplied to thetub 52 is discharged to the outside through the drainage device 60.

Thereafter, in the rinsing operation, rinse water is supplied to the tub52, and the drum 54 is rotated by the driving device 56, thereby rinsingthe laundry.

In the rinsing operation, in the same manner as the washing operation,when the rinse water is supplied to the tub 52, the rinse water can besupplied through the water supply device 58, or the water drop supplydevice 82 and the circulation channel 72. Further, in order to easilyrinse the laundry in the rinsing operation, steam or hot wind can besupplied to the tub 52 through the heating apparatus 70.

The above rinsing operation may be repeated plural times, and wheneverthe rinsing operation of each cycle is completed, the rinse water of thetub 52 is discharged to the outside through the drainage device 60.

The washing machine comprising the above heating apparatus 70 canperform a drying operation for drying the wet laundry placed in the drum54 using hot wind produced by the heating apparatus.

That is, when the wet laundry is placed in the drum 54 and the dryingoperation is performed, hot wind is produced by the heating apparatus70, and supplied to the tub 52. Then, moisture of the wet laundry placedin the drum 54 is evaporated by the hot wind supplied to the tub 52,thus drying the laundry of the drum 54. Here, the drainage device 60 isoperated so that water is not collected in the bottom of the tub 52.

As apparent from the above description, the present invention provides aheating apparatus of a washing machine, which supplies steam or hot windto an upper part of a tub in a washing or rinsing operation so as todirectly heat wash water and laundry, and a washing method thereof,thereby reducing the time taken to perform the washing or rinsingoperation and an energy consumption rate, and improving a washingcapacity.

Further, the heating apparatus of the present invention produces hotwind in the same manner as the washing or rinsing operation and suppliesthe hot wind to the tub so as to dry the wet laundry, therebydiversifying its function without additional cost and minimizingproduction costs.

Although the preferred embodiment of the present invention has beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A heating apparatus of a washing machine comprising: a circulationchannel for connecting one side of a tub to the other side of the tub sothat air of the tub is circulated therethrough; an air blower installedin the circulation channel for generating air-blowing force; a heaterinstalled in the circulation channel for heating air of the circulationchannel; and water drop scattering device installed in the circulationchannel for scattering water drops in air blown by the heater so thatsteam is supplied to the tub.
 2. The heating apparatus as set forth inclaim 1, wherein the circulation channel includes: a condensing ductconnected to one side of the tub for condensing the air of thecirculation channel; and a drying duct connecting the condensing duct tothe other side of the tub and including the heater installed therein. 3.The heating apparatus as set forth in claim 2, wherein the water dropscattering device is installed in the condensing duct.
 4. The heatingapparatus as set forth in claim 1, wherein the water drop scatteringdevice includes: water drop supply device including a nozzle forspraying water drops into the circulation channel; and an orificeinstalled in the circulation channel for scattering the water dropssupplied into the circulation channel.
 5. The heating apparatus as setforth in claim 4, wherein the orifice is obtained by forming aprotrusion along the inner wall of the air blower.
 6. The heatingapparatus as set forth in claim 4, wherein the orifice has a shape suchthat the width of the orifice is gradually narrowed and then graduallybroadened in the direction of blowing air of the air blower.
 7. Theheating apparatus as set forth in claim 1, wherein the water dropscattering device is located in front of the air blower in the directionof blowing air of the circulation channel.
 8. A heating apparatus of awashing machine comprising: a condensing duct connected to one side of atub; a drying duct connecting the condensing duct to the other side ofthe tub, and including a heater installed therein; an air blower forgenerating air-blowing force in the direction from the condensing ductto the drying duct; a nozzle installed in the condensing duct forspraying water into the condensing duct; and water drop scatteringdevice installed in the condensing duct, and including an orifice forscattering the water sprayed into the condensing duct.
 9. The heatingapparatus as set forth in claim 8, wherein the orifice has a shape suchthat the width of the orifice is gradually narrowed and then graduallybroadened in the direction of blowing air of the air blower.
 10. Awashing method of a washing machine comprising: circulating air of a tubinto a circulation channel in a washing or rinsing operation, andspraying and scattering water in a dropping state into the circulationchannel; producing steam by operating a heater installed in thecirculation channel; and supplying the steam to the tub.
 11. The washingmethod as set forth in claim 10, further comprising: supplying a largerquantity of water in a drying operation to the circulation channel thanthat of the washing or rinsing operation during the circulation of theair of the tub into the circulation channel; condensing the air of thecirculation channel using the supplied water, and producing hot wind byheating the condensed air using the heater; and supplying the hot windto the tub.
 12. The washing method as set forth in claim 11, wherein thevelocity of air blown into the circulation channel when the steam issupplied to the tub is higher than the velocity of air blown into thecirculation channel when the hot wind is supplied to the tub.
 13. Thewashing method as set forth in claim 10, wherein wash water is suppliedto the tub through the circulation channel in the washing or rinsingoperation.
 14. A washing method of a washing machine comprising:circulating air of a tub into a circulation channel in a washing orrinsing operation; heating the air of the circulation channel to producehot wind; and supplying the hot wind to the tub.
 15. The washing methodas set forth in claim 14, wherein wash water is supplied to the tubthrough the circulation channel in the washing or rinsing operation. 16.The washing method as set forth in claim 14, further comprising dryinglaundry of the tub using the hot wind in a drying operation.
 17. Thewashing method as set forth in claim 14, wherein water drops are sprayedselectively into the circulation channel and scattered so that steam issupplied to the tub.
 18. The washing method as set forth in claim 17,wherein the velocity of air blown into the circulation channel when thesteam is supplied to the tub is higher than the velocity of air blowninto the circulation channel when the hot wind is supplied to the tub.19. The washing method as set forth in claim 17, wherein a largerquantity of water when the hot wind is supplied to the tub is suppliedto the circulation channel than when the water drops are sprayed intothe circulation channel.
 20. The washing method as set forth in claim17, further comprising drying laundry of the tub using the hot wind in adrying operation.